Assessment of Transcranial Alternating Current Stimulation's Clinical Efficacy in Treating Cognitive Impairment of Idiopathic Inflammatory Demyelinating Diseases

This study tests a non-invasive brain stimulation technique called transcranial alternating current stimulation (tACS) to see if it can improve thinking and memory problems in people with inflammatory brain diseases such as multiple sclerosis or neuromyelitis optica spectrum disorder. **You may be eligible if...** - You are 18–60 years old - You have been diagnosed with multiple sclerosis, neuromyelitis optica spectrum disorder, or another central nervous system inflammatory demyelinating disease - Your medications have been stable for at least 3 months - You have measurable cognitive (thinking/memory) difficulties **You may NOT be eligible if...** - You have metal implants in your skull or a pacemaker - You have a history of epilepsy or seizures - You are pregnant - You have significant uncontrolled psychiatric conditions Talk to your doctor to see if this trial is right for you.